Electric discharge device



Oct. 30, D, L SMART ELECTRIC DISCHARGE DEVICE 7 Filed 001;. 20, 1949 9M gel/val L v/mva/df fiy/dMi/JM FIG. 2

l I 1 z 1 FIG; I.

Patented Oct. 30, 1951 to The English Electric Company Limited, London, England, a British company Application October 20, 1949, Serial No. 122,461

7 In Great Britain October 25, 1948 8 Claims. (Cl. 313-170) This invention relates to electric discharge devices of the kind employing. a liquid pool cathode and in which the main discharge is initiated by a subsidiary discharge taking place between the cathode and a movable ignition electrode.

. In the past such an ignition electrode has been fomed by or mounted on 'a movable or pivoted member arranged in a special side arm of the device, a coil being" provided for magnetically influencing the member,

In order that the power required for moving I the ignition and excitation electrode may be kept low, it is desirable that it should be almost balanced about a pivot, and it is convenientto lead the ignition current through the pivot of the ignitiOn electrode. A difficulty, however, is that in the course of time one or other of the rela- "tively movable portions of the pivot may become pitted, due to arcing, and the pivot is then apt to stick inone position.

According to a feature of the invention the pivot is formed of relatively movable elements having sufficient play to permit one element to roll upon the other in the operation of the ignition electrode.

In apreferred form of the invention the pivoted member is formed of a strip of metal doubled upon itself to provide a pair of parallel arms, each of-the arms being provided with a pivot hole and a metallic pin supported from the envelope of the .device passes through these holes with suflicient clearance to permit a rolling'contact between the edges of the holes and the pin.

In an alternative form of the invention the pivoted member is provided with a pin extending therefrom and engaging in pivot holes in a pair of spaced supports.

According to a further feature of the invention the two elements of the pivot are of material or are covered with a thin layer of material which wets with the liquid cathode material so that a conducting layer of the latter is formed at least at the points of contact of the two elements. The elements of the pivot may also be arranged so that one of them forms a receptacle for a portion of the cathode material, on which portion the other element floats.

Several forms of the invention will now be described with reference to the accompanying drawings.

In these drawings Fig. 1 illustrates a portion of a discharge device incorporating a particular form of the invention. The discharge device is of the type known as an Excitron and has a glass envelope I containing an anode and grid,

and a cathode consistin of a pool of mercury 2. An ignition electrode consisting of a graphite rod 3 is arranged within the envelope on a pivoted 'arm 4 so that it may be moved into or out of contact with the cathode 2. The arm 4 consists of a strip of metal bent double to hold the electrode 3 at one end and to provide at the other end two spaced parallel members, one of which is shown at 4a, each formed with a hole 5., A supporting and current conducting wire'B has a bent-over portion 6a which passes through the holes 5 and serves as a pivot pin. The portion Ed has a diameter about two thirds of that 10f the holes '5. A'lead-in wire 1 which is provided with vitreous insulation 8 'and is sealed to an eyelet 9 Welded to a metal portion of the envelope supports the wire 6 by means of a metal clip In. Additional rigidity is provided by a further clip I I secured to an electrode I2 of the device and engaging a glass bead l3 which surrounds an extension 6bof the wire 6.

A strip of iron I4 is welded to the end of the arm 4 to form an armature and is folded round a weight l5 which partially balances the'electrode 3 and'the other end of the arm 4 so as to reduce to a minimum the energy necessary for operation. A D. C. choke I6 is arranged outside the envelope l in such a way that its magnetic field extends to the position occupied by the upper endof the armature H. In .order to increase the strength of. the field which influences the armature l4, the gap ll of the choke is arranged adjacent this position.

Ignition current is supplied to the electrode 3 through the lead-in wire I and the choke I6 is included in series to provide smoothing. The electrode 3 is normally held by its own weight in contact with the mercury cathode 2 but when the ignition circuit is energised, current begins to flow and the magnetic circuit of the choke I6 becomes efiective to attract the armature l4 towards the wall of the envelope I, bringing the parts into the position shown in the drawing, and resulting in the formation of an arc between the electrode 3 and the cathode 2. A D. C. potential is used to supply the ignition circuit and the arc is maintained after ignition to serve as an excitation are.

It will be seen that the ignition and excitation current is supplied through the pivot of the arm 4 and in normal operation pitting of the metal surfaces at this point is to be expected. Since, however, the holes 5 are considerably larger than the pin 6a, any pitting which may take place will have negligible effect on the satisfactory movement of the arm 4. Furthermore, the arm 4 and the pin Ba are both plated with a material which wets with mercury so that the contact between the two parts is improved and arcing reduced and there will thus be less likelihood of pitting occurring.

Fig. {2. cof athe' =drawings illustrates-adiagrammatically a *further:- form of ignition ide'vice. this case the electrode 3 is arranged on the same side of the pivot as the armature l4, being supported from the latter on anlarmvib. The

armature I4 is carried as before onapivotedarm 4 and in this case a balancesweight.15-.iaamanaed 1 at the end of the arm 4 whichiixeremoite=from-athe armature l4 and beyond the pivot 5. Thea-balance weight I5 is chosen so aas. tqpermit the, electrode 3 normally to dip intothe cathode-2. flhe electrode 3 is withdrawn from. the cathode 2 when a coil (not shown) arranged on the outside-of ?the envelope I is energized.

:Whatzl claim easymy :inventionzand desire: :to rsecurezbyLettersfiatentis; V r 7 1. z-An electric;dischargedevicaincludingeat least nanzanodeaa poolrcathodeeand an-gexeitaticn relee- ;tr,elde; normally in contact awith-athesr-material-rof SaidfiCathOQE-YblIt arrangedafor-L movement away from said-\materialr-underethe influence Lofia lmag- 1- inetic1 fieldrextending ithroughfla-wall, of -the device,

saidaeleqtrode beingrmounted von a pivot i formed a 5:; of =.-:relatively: movable elements. haying. suflicient gplay ito permit lone}element to rolhuponi the other lin the eperationrofthegexcitationelectrode. a a 1 2.:Air;electricdischarge.devieeflas claimed, in Qclaim l,rawhereinasaid pivot' is included in the aconducting, path ,fOl'a currentsupplied .toi fsaidjlconv.trolelectrode.

3. An electric .disrihargeQdevice o. including .at least an anodepa poolicatho'denan'dlan excitation velectrode normally in contact with. thetmaterial ,ofisaidratho delbutarrangedsfor movement away from said cathode under lthe'inflilenceidiama .netic field extending through: a .wallroi the device, said electrode bein supported by V a pivctiformed v. of .twoirelatively. movableleljements having sufli- .cient play to permit one-.ofn sai'd elementsztogroll upon .theotherithe .operationrof .ithel excitation i.electrodeaandeatjleast the contacting surfaces .of =sai'd. elements-being of 'amaterialwhich welts, with .Lthe materialbi said cathode. .i Angelectric .dischargegfdevice as 'claimed'in iclaimfi wherein said ipivotiisiincluded in'the conducting pathfor current supplied toesaid control electrode. .5 An electric. discharge device "including "at V 4 7 least an anode, a pool cathode and an excitation electrode normally in contact with the material of said cathode but arranged for movement away from said material under the influence of a mag- 5 netic field extending through a wall of said device,

said electrode being carried by a pivoted structureiinzthe iormiof twolspacedzsubstantially parv.allel metal stripfs provided'ewith apertures through which extends a fixed supporting rod serving as gpart of the pivot and as a current conductor for 7 said excitation electrode, said apertures being of sensibly -g-rea-ter diameter than said supporting rod. a

';6'.,@An ,e' ;citat;ion electrode for a pool cathode eelectricrdischargezdevice including a member pivoted for movement into and out of the cathode .material,;said-=member being mounted on a current-carrying pivot formed of relatively movable elements having sufficientplay to permit one ele- 0 ment to roll upon the other in operation of said ,electrode.

.atlleast.- the contacting surfaces. oi, said elements ,are.. of,,almaterial which .Wets with the, material of said-cathode.

40 UNITED STATES IBAI'ENIS Number v 7 Name Date- 11398940 -M-oyer et al. iApr; '23, 1935 2;19 2;506 rRu'ben -J-Mar351'1940 FOREIGN PATENTS i-lumber J Country fIDate 94:31.7 (Switzerland. .:;Apr.:1 @922 1376 807 wGermany .May :1929 m $345,969 rGrreataBritain Sept;: 26,-:1-929 567,471 1: Germany Decrzl5; l9,32 13423642 IGr-eatrBritain. 'Feb.5 @1931 V I Swit/zer1anrl room 1937 

